CCDC181, a kinocilium-localization protein, is dispensable for hair bundle development and auditory perception

Inner ear cochlear hair cells exhibit a highly specialized ciliary architecture that consists of a bundle of stereocilia responsible for mechanotransduction and, during development, a single kinocilium that governs hair bundle polarity. While the morphogenesis of stereocilia is being extensively characterized and many key molecules have been identified, the molecular mechanisms governing the formation and subsequent degeneration of the kinocilium remain largely unknown. Through immunohistochemical staining, we found that CCDC181, a microtubule-binding protein, is abundantly expressed in the postnatal cochlear hair cells and specifically localized to the kinocilium. To investigate its function in cochlear hair cell morphogenesis and auditory perception, we generated a Ccdc181 knockout mouse. Hair cell morphology was characterized by using immunostaining and electron microscopy, and auditory function was then evaluated by measuring auditory brainstem responses. Our data suggests that loss of CCDC181 has minimal effects on kinocilium morphogenesis, hair cell polarity, and normal hearing in mice.